1. Field of the Invention
The present invention relates to a method and an apparatus for configuring a control channel in a wireless communication system. More particularly, the present invention relates to a method and an apparatus for reconfiguring a control channel considering the effects of interference.
2. Description of the Related Art
Next-generation communication systems have evolved into mobile communication systems that provide User Equipments (UEs) with services capable of high-speed, high-capacity data transmission.
The recent increase in demand for data services may hardly be met by the cell splitting technology of the related art. Therefore, the next-generation mobile communication systems, such as Long Term Evolution (LTE) and LTE-Advanced (LTE-A), have been proposed for servicing small indoor/outdoor areas using micro evolved Node Bs (eNBs) having cell coverage areas smaller than that of macro eNBs. The micro eNB may refer to all types of cells, including a femto cell, a pico cell, a relay node, a radio repeater, and the like. Compared with a network of macro cells, a network of micro cells is considered a heterogeneous network capable of increasing the capacity with low cost, and the heterogeneous network is one of the major evolutionary technologies under discussion in the next-generation mobile communication systems.
However, the heterogeneous network may suffer from many problems, such as cell identification difficulty due to the lack of cell Identifiers (IDs), and coverage area imbalance between an uplink and a downlink because of the different transmission powers of cells. More particularly, the interference problem between heterogeneous cells, such as interference between macro cells and micro cells, is one of the most significant problems the heterogeneous network now faces.
FIG. 1 is a diagram illustrating an interference problem between heterogeneous cells according to the related art. An interference problem between a macro cell and micro cells will be described with reference to FIG. 1.
Referring to FIG. 1, interference problems in a heterogeneous network may be roughly divided into two types. For example, an eNB and a UE of a macro cell 110 will be referred to as a macro eNB 111 and a macro UE 113, respectively, while eNBs and UEs of micro cells will be referred to as micro eNBs 131 and 151, and a micro UE 153, respectively.
For example, as for one of the interference problems, the micro UE 153 connected to the micro eNB 151 forming a pico cell 150 may be affected by transmission signals of the macro eNB 111. The macro eNB 111 is far greater than the micro eNB 151 in terms of transmission power, so the macro eNB 111 has a coverage area broader than that of the micro eNB 151. In this case, the micro UE 153 connected to the micro eNB 151 may be affected significantly by the signals received from the macro cell 110.
As for the other interference problem, the macro UE 113 connected to the macro eNB 111 may be affected by transmission signals of the micro eNB 131 forming a femto cell. A cell 130 of the micro eNB 131 may be a Closed Subscriber Group (CSG) cell like a femto cell. In this case, the macro UE 113 may be affected by the signals transmitted from the micro eNB 131 because the macro UE 113 cannot access the micro eNB 131 even though it is located close to the micro eNB 131.
As described above, a macro UE connected to a macro cell may be affected by signals from a micro cell, while a micro UE connected to a micro cell may be affected by signals from a macro cell. This interference problem may interfere especially with the stable reception of a control channel. In the LTE-A system, introduction of an Extended-Physical Downlink Control Channel (E-PDCCH) has been proposed to address the interference problem in a control channel region, such as a PDCCH.
FIG. 2 illustrates control channel reconfiguration from a PDCCH to an E-PDCCH according to the related art.
Referring to FIG. 2, reference numeral 210 represents a PDCCH region for transmission of downlink control information, and reference numeral 230 represents a Physical Downlink Shared Channel (PDSCH) region for transmission of downlink data. The LTE-A system may allocate control information for a UE to an E-PDCCH region 231 in the PDSCH region 230, for its transmission in the heterogeneous network environment. In order for the E-PDCCH to be supportable in the PDSCH region 230, effective reconfiguration of a control channel from the existing PDCCH region 210 to the E-PDCCH region 231 is required. The need for the reconfiguration process from the PDCCH region 210 to the E-PDCCH region 231 arises even in a PDCCH reconfiguration process between Carrier Components (CCs) of a carrier aggregation scheme, which is another technology presently proposed as the major technology in the next-generation communication system like the LTE-A system.
FIG. 3 illustrates inter-CC PDCCH reconfiguration in carrier aggregation according to the related art.
Referring to FIG. 3, when a UE using a CC1 PDCCH region 301 desires to move its CC to a CC2 PDCCH region 303, a reconfiguration process for a control channel from the CC1 PDCCH region 301 to the CC2 PDCCH region 303 is required.
Many studies have been conducted to reconfigure a control channel considering the interference problems in the control channel region. This control channel reconfiguration is more required to cope with interference between heterogeneous cells, like interference between a macro cell and a micro cell. For the control channel reconfiguration, an efficient signaling procedure is required between a UE and an eNB.
Therefore, a need exists for a method and an apparatus for efficiently performing control channel reconfiguration in a wireless communication system.